never used a vac canopy before, have heard ordinary polystyrene and superglue can stuff them. if so what do you use.

I very seldom use the kit injected canopies. They're too thick. So I have alot of experience with vac canopies and the very best way to glue them to the airframe is with white glue. Elemor's, Krista Klear or something like that. If you need to thin it, use Diet Sprite or Diet Seven-Up. It's really sticky stuff and clear!!
Most of the time, I stretch sprue into thin rods, and glue them to the airframe about the thickness of the vac canopy from the edge. This will give you a bit more surface area for the white glue to adhere to.
Do NOT try to sand away the excess. Instead, use a wet finger to wipe it away and blend it in where needed. Also, you can use a lint free rag wrapped tightly around your finger and wet it in clean water. This will clean any residue off the model and now it's ready for paint!!
BTW, I've NEVER had one to come off when removing the canopy mask!!
Bo Roberts

What Jabow1 said is pretty much spot on - the only thing i can add is that I like to use moistened Q-tips instead of my fat fingers for scrubbing away excess white glue.